Depuis 2004, les rovers Spirit et Opportunity de la mission MER (Mars Exploration Rover) explorent leurs sites d'atterrissage respectifs, le cratère Gusev et les plaines de Meridiani. Ces travaux de thèse portent sur l'analyse et l'interprétation des données de l'instrument APXS (Alpha-Particle X-ray Spectrometer), situé au bout du bras articulé de chacun des rovers, dont le rôle est de déterminer la composition chimique des roches et des sols martiens par spectrométrie X. Grâce à leur surprenante longévité, Spirit et Opportunity ont pu s'éloigner à plusieurs km de leurs lieux d'atterrissage initiaux et les APXS ont analysé de nombreux échantillons fournissant des indices sur le rôle que l'eau a pu jouer dans le passé martien. J'ai d'abord choisi d'étudier cette diversité d'échantillons à l'aide d'une approche d'analyse multidimensionnelle. Ceci m'a permis de réaliser une classification des échantillons et de mettre en évidence les relations pétrogénétiques entre les roches et les sols de Gusev et Meridiani. Je présenterai les principaux résultats obtenus grâce à cette méthode ainsi que leur lien avec l'organisation spatiale et stratigraphique des échantillons. Je montrerai ensuite comment ces résultats m'ont incité à tester un modèle géochimique numérique d'altération de basalte martien par un brouillard acide de SO3. Je décrirai les hypothèses de ce modèle avant d'en comparer les résultats avec les données MER. Nous verrons enfin quelles en sont les implications, au niveau de la géologie des sites de Gusev et Meridiani et plus généralement vis-à-vis de l'histoire géologique de Mars et des conditions qui ont prévalu à sa surface dans le passé.

The growing need for designing and implementing reliable voice-based human-machine interfaces has inspired intensive research work in the field of voice-enabled systems, and greater robustness and reliability are being sought for those systems. Speech recognition has become ubiquitous. Automated call centers, smart phones, dictation and transcription software are among the many systems currently being designed and involving speech recognition. The need for highly accurate and optimized recognizers has never been more crucial. The research community is very actively involved in developing powerful techniques to combine the existing feature extraction methods for a better and more reliable information capture from the analog signal, as well as enhancing the language and acoustic modeling procedures to better adapt for unseen or distorted speech signal patterns. Most researchers agree that one of the most promising approaches for the problem of reducing the Word Error Rate (WER) in large vocabulary speech transcription, is to combine two or more speech recognizers and then generate a new output, in the expectation that it provides a lower error rate. The research work proposed here aims at enhancing and boosting even further the performance of the well-known Recognizer Output Voting Error Reduction (ROVER) combination technique. This is done through its integration with an error filtering approach. The proposed system is referred to as cROVER, for context-augmented ROVER. The principal idea is to flag erroneous words following the combination of the word transition networks through a scanning process at each slot of the resulting network. This step aims at eliminating some transcription errors and thus facilitating the voting process within ROVER. The error detection technique consists of spotting semantic outliers in a given decoder's transcription output. Due to the fact that most error detection techniques suffer from a high false positive rate, we propose to combine the error filtering techniques to compensate for the poor performance of each of the individual error classifiers. Experimental results, have shown that the proposed cROVER approach is able to reduce the relative WER by almost 10% through adequate combination of speech decoders. The approaches proposed here are generic enough to be used by any number of speech decoders and with any type of error filtering technique. A novel voting mechanism has also been proposed. The new confidence-based voting scheme has been inspired from the cROVER approach. The main idea consists of using the confidence scores collected from the contextual analysis, during the scoring of each word in the transition network. The new voting scheme outperformed ROVER's original voting, by up to 16% in terms of relative WER reduction.

H συγκεκριμένη διπλωματική εργασία αποτελεί συνέχεια μιας σειράς διπλωματικών εργασιών οι οποίες είχαν ως πηγή έμπνευσης το ρομποτικό όχημα (robot rover) Sojourner το οποίο είχε σταλθεί στον πλανήτη Άρη από τη NASA το 1997. Συγκεκριμένα είχε υλοποιηθεί παλαιότερα μια διπλωματική εργασία στην οποία σκοπός ήταν η κατασκευή ενός ενσωματωμένου συστήματος και του αντίστοιχου οχήματος που θα ελέγχεται στα πρότυπα του ρομποτικού οχήματος Sojourner, όσο αυτό είναι εφικτό. Πιο συγκεκριμένα είχε κατασκευαστεί ένα όχημα και είχε γίνει ο σχεδιασμός και η υλοποίηση ενός ενσωματωμένου συστήματος βασισμένο στον επεξεργαστή της Intel 8086. Σκοπός στη συγκεκριμένη διπλωματική εργασία, είναι ο σχεδιασμός και η υλοποίηση ενός ενσωματωμένου συστήματος, το οποίο θα στηρίζεται σε ένα πιο σύγχρονο υπολογιστικό σύστημα και ταυτόχρονα η υλοποίηση ενός μηχανισμού, με τον οποίο το όχημα θα μπορεί να ανιχνεύει στοιχειωδώς την ύπαρξη κάποιου πιθανού εμποδίου. Αρχικά επιλέχθηκε να υλοποιηθεί μηχανισμός στερεοσκοπικής όρασης προκειμένου να πραγματοποιείται η αναγνώριση πιθανού εμποδίου. Η επιλογή αυτή αποτέλεσε σημαντικό παράγοντα για τον μετέπειτα προγραμματισμό του συστήματος. Στη συνέχεια έγινε ο σχεδιασμός του ενσωματωμένου συστήματος και η επιλογή του hardware που το απαρτίζει. Οι επιλογές που έγιναν προσπάθησαν να αντισταθμίσουν τους παράγοντες κόστους και ταχύτητας. Το επόμενο βήμα αποτέλεσε η software υλοποίηση, δηλαδή ο προγραμματισμός του ενσωματωμένου συστήματος. Αρχικά υλοποιήθηκαν οι ρουτίνες για την κίνηση. Κατόπιν αναπτύχθηκε το πρόγραμμα που αφορά την στερεοσκοπική όραση και στο τέλος έγινε ο προγραμματισμός του radio module. Στη συνέχεια συνδυάστηκαν όλα τα παραπάνω μαζί ώστε να αποτελέσουν την τελική εφαρμογή. Στο τέλος πραγματοποιήθηκε η αξιολόγηση της επιλογής του υπολογιστικού συστήματος που χρησιμοποιήθηκε, καθώς και εξήχθησαν συμπεράσματα για πιθανές μελλοντικές προσθήκες και δυνατότητες. / This diploma thesis belongs to a series of diploma theses, which were inspired by NASA’s robot rover Sojourner which had been sent on Mars in 1997. Specifically, in an older diploma thesis, an embedded system was designed and implemented in order to move and control a vehicle, like it had been done with Sojourner, in a feasible degree. More specifically, a vehicle was constructed and an embedded system which was based on Intel 8086 processor was designed and implemented. The goal of this diploma thesis is the design and implementation of an embedded system which is based on a modern computer system. Moreover a mechanism for elementary locating a possible obstacle was implemented. In the first stage, stereo vision was chosen to be the process in which the vehicle would recognize a possible obstacle. That choice was a significant factor for the later system programming. Afterwards, the hardware that is used on the vehicle was chosen. Those choices tried to have a trade-off between cost and performance. The next step was the programming of the embedded system. This step consisted of three more steps. In the first step, movement functions which were responsible for moving the vehicle were programmed. Secondly, the program responsible for stereo vision was also written and the third step was the programming of the radio module which was used. Finally, all those three programs were combined in order to produce the final application. In the end, we assessed the choice of the computer system we used as well as the whole system and we reached on some conclusions. Also, some suggestions for future additions were introduced.

The Alpha Particle X-ray Spectrometer (APXS) on the Mars Exploration Rovers possesses the ability to detect carbon and oxygen within martian samples via Rutherford backscattering principles. Several consecutive measurements of the martian atmosphere by Spirit, paralleled by Monte Carlo simulations, provided an energy calibration to mitigate the absence of an alpha-mode calibration pre-flight. Data from a pre-flight thermal acceptance test agreed with this energy calibration, confirming the presence of an unexpected offset. Correcting a bug in the APXS firmware resulted in a temperature-independent energy scale. A model was developed and applied to all atmospheric data illustrating a dip in atmospheric peak areas, potentially arising from a week-long weather event on Mars. An early expansion of this model to solid samples has not yet been able to detect any hydrated minerals or carbonates. Preliminary investigations into determining martian atmospheric pressure and potential elemental layering within samples shows promise.

The cosmic “Dark Ages” is the cosmic era between the epochs of recombination of cosmic microwave background and the formation of the first stars. The only signal from this epoch is from neutral hydrogen, which could represent one of the richest data sets in cosmology. In order to extract this data, NASA/JPL has proposed a rover mission to the farside of the moon to deploy several radio arrays. Here the arrays would gather data undisturbed by human interference. This thesis examines the possibility of using photovoltaic and electric batteries as an energy solution for a rover on the moon. The requirement for such a system to survive on the moon is discussed in a literature study. A proof of concept simulation using a Simulink model has also been done. The thesis concludes that a rover can deploy the radio array using solar energy. It would be able to hibernate through the night using radioisotope heating. It would need to wait for its batteries to charge before each night. / I kosmologi kallas epoken mellan “rekombinationen till väte” och bildandet av de första stjärnorna för “den mörka tidsåldern”. Från denna tid finns endast spår i form av strålning från neutralt väte. Denna strålning kan enligt astronomer vara en viktigare källa till data om universums uppkomst än den kosmiska mikrovågsstrålningen. Därför arbetar NASA/JPL med att hitta metoder att observera denna rika källa till data. Den mest använda metoden är att använda lågfrekventa radioteleskop för att observera strålning med våglängder mellan 3-30 m och frekvenser mellan 10-100 Mhz. Ett stort problem med så kort strålning är den lätt störs ut av mänsklig påverkan och andra radiokällor, tillexempel solen. Ett sätt att undvika antropogen störning är att bygga ett radioteleskop på månens baksida. Eftersom månen är i en låst bana runt jorden vänder den alltid samma sida bort från planeten. Därför är platsen alltid i radioskugga från jorden ochstörs inte av mänsklighetens radiotrafik. JPL har lång erfarenhet av användandet av robotfarkoster för att utforska himlakroppar. År 2030 vill de sända en så kallad rover för att upprätta en grupp radioteleskop på månen med syftet att införskaffa data om “den mörka tidsåldern.” Högskolan i Halmstad erbjuder sedan 2013 studenter möjligheten att skriva sitt examensarbete i samarbete med NASA/JPL om konstruktionen av denna rover. Detta arbete har ämnat finna en lösning på rovens energiförsörjning genom att använda solceller och batterier. Slutsatsen har varit att det är möjligt att driva en rover på månen med solceller samt batterier. Ett krav är att rovern värms med radioisotoperunder natten för att minska energianvändningen.

Most current space robotics vehicles use solar energy as their prime energy source. In spherical robotic vehicles the use of solar cells is very restricted. Focusing on the particular problem, an improved method to generate electrical power will be developed; the innovation is the use of an internal pendulum-generator mechanism to generate electrical power while the ball is rolling. This concept will enable spherical robots on future long-duration planetary exploration missions. Through a developed proof-of-concept prototype, inspired by the Russian thistle plant, or tumbleweed, this thesis will demonstrate power generation capabilities of such a mechanism. Furthermore, it will also present and validate a parametric analytical model that can be used in future developments as a design tool to quantify power and define design parameters. The same model was used to define the design parameters and power generation capabilities of such a system in Martian environment.

Most current space robotics vehicles use solar energy as their prime energy source. In spherical robotic vehicles the use of solar cells is very restricted. Focusing on the particular problem, an improved method to generate electrical power will be developed; the innovation is the use of an internal pendulum-generator mechanism to generate electrical power while the ball is rolling. This concept will enable spherical robots on future long-duration planetary exploration missions. Through a developed proof-of-concept prototype, inspired by the Russian thistle plant, or tumbleweed, this thesis will demonstrate power generation capabilities of such a mechanism. Furthermore, it will also present and validate a parametric analytical model that can be used in future developments as a design tool to quantify power and define design parameters. The same model was used to define the design parameters and power generation capabilities of such a system in Martian environment.

The growing need for designing and implementing reliable voice-based human-machine interfaces has inspired intensive research work in the field of voice-enabled systems, and greater robustness and reliability are being sought for those systems. Speech recognition has become ubiquitous. Automated call centers, smart phones, dictation and transcription software are among the many systems currently being designed and involving speech recognition. The need for highly accurate and optimized recognizers has never been more crucial. The research community is very actively involved in developing powerful techniques to combine the existing feature extraction methods for a better and more reliable information capture from the analog signal, as well as enhancing the language and acoustic modeling procedures to better adapt for unseen or distorted speech signal patterns. Most researchers agree that one of the most promising approaches for the problem of reducing the Word Error Rate (WER) in large vocabulary speech transcription, is to combine two or more speech recognizers and then generate a new output, in the expectation that it provides a lower error rate. The research work proposed here aims at enhancing and boosting even further the performance of the well-known Recognizer Output Voting Error Reduction (ROVER) combination technique. This is done through its integration with an error filtering approach. The proposed system is referred to as cROVER, for context-augmented ROVER. The principal idea is to flag erroneous words following the combination of the word transition networks through a scanning process at each slot of the resulting network. This step aims at eliminating some transcription errors and thus facilitating the voting process within ROVER. The error detection technique consists of spotting semantic outliers in a given decoder's transcription output. Due to the fact that most error detection techniques suffer from a high false positive rate, we propose to combine the error filtering techniques to compensate for the poor performance of each of the individual error classifiers. Experimental results, have shown that the proposed cROVER approach is able to reduce the relative WER by almost 10% through adequate combination of speech decoders. The approaches proposed here are generic enough to be used by any number of speech decoders and with any type of error filtering technique. A novel voting mechanism has also been proposed. The new confidence-based voting scheme has been inspired from the cROVER approach. The main idea consists of using the confidence scores collected from the contextual analysis, during the scoring of each word in the transition network. The new voting scheme outperformed ROVER's original voting, by up to 16% in terms of relative WER reduction.

Wheel slip is a common problem in planetary rover exploration tasks. During the current Mars Exploration Rover (MER) mission, the Spirit rover almost became trapped on a dune because of wheel slip. As rover missions on harsh terrains expand in scope, mission success will depend not only on rover safety, but also alacrity in task completion. Speed combined with exploration of varied and difficult terrains, the risk of slip increases dramatically. We first characterize slip performance of a rover on harsh terrains by implementing a novel High Fidelity Traversability Analysis (HFTA) algorithm in order to provide slip prediction and detection capabilities to a planetary rover. The algorithm, utilizing path and energy cost functions in conjunction with simulated navigation, allows a rover to select the best path through any given terrain by predicting high slip paths. Integrated software allows the rover to then accurately follow a designated path while compensating for slippage, and reach intended goals independent of the terrain over which it is traversing. The algorithm was verified using ROAMS, a high fidelity simulation package, at 3.5x real time speed. We propose an adaptive path following algorithm as well as a human-trained neural network to traverse multiple harsh terrains using slip as an advantage. On a near-real-time system, and at rover speeds 15 times the current average speed of the Mars Exploration Rovers, we show that the adaptive algorithm traverses paths in less time than a standard path follower. We also train a standard back-propagation neural network, using human and path following data from a near-real-time system. The neural network demonstrates it ability to traverse new paths on multiple terrains and utilize slip to minimize time and path error.

abstract: In-situ exploration of planetary bodies such as Mars or the Moon have provided geologists and planetary scientists a detailed understanding of how these bodies formed and evolved. In-situ exploration has aided in the quest for water and life-supporting chemicals. In-situ exploration of Mars carried out by large SUV-sized rovers that travel long distance, carry sophisticated onboard laboratories to perform soil analysis and sample collection. But their large size and mobility method prevents them from accessing or exploring extreme environments, particularly caves, canyons, cliffs and craters. This work presents sub- 2 kg ball robots that can roll and hop in low gravity environments. These robots are low-cost enabling for one or more to be deployed in the field. These small robots can be deployed from a larger rover or lander and complement their capabilities by performing scouting and identifying potential targets of interest. Their small size and ball shape allow them to tumble freely, preventing them from getting stuck. Hopping enables the robot to overcome obstacles larger than the size of the robot. The proposed ball-robot design consists of a spherical core with two hemispherical shells with grouser which act as wheels for small movements. These robots have two cameras for stereovision which can be used for localization. Inertial Measurement Unit (IMU) and wheel encoder are used for dead reckoning. Communication is performed using Zigbee radio. This enables communication between a robot and a lander/rover or for inter-robot communication. The robots have been designed to have a payload with a 300 gram capacity. These may include chemical analysis sensors, spectrometers and other small sensors. The performance of the robot has been evaluated in a laboratory environment using Low-gravity Offset and Motion Assistance Simulation System (LOMASS). An evaluation was done to understand the effect of grouser height and grouser separation angle on the performance of the robot in different terrains. The experiments show with higher grouser height and optimal separation angle the power requirement increases but an increase in average robot speed and traction is also observed. The robot was observed to perform hops of approximately 20 cm in simulated lunar condition. Based on theoretical calculations, the robot would be able to perform 208 hops with single charge and will operate for 35 minutes. The study will be extended to operate multiple robots in a network to perform exploration. Their small size and cost makes it possible to deploy dozens in a region of interest. Multiple ball robots can cooperatively perform unique in-situ science measurements and analyze a larger surface area than a single robot alone on a planet surface. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2016